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DESTE GÖKAY, GONCA

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DESTE GÖKAY

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GONCA

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Now showing 1 - 10 of 10
  • Publication
    Evaluation of physical properties of polyamide and methacrylate based denture base resins polymerized by different techniques
    (Wolters Kluwer Medknow Publications, 2021-12-01) Gökay, Gonca Deste; Durkan, R.; Oyar, P.; DESTE GÖKAY, GONCA; 0000-0002-5481-0063; AAM-7219-2020
    Aim: This study aims to comparatively evaluate the flexural strength, internal adaptation, elastic modulus, and maximum deflection of a newly introduced, strengthened injection-molded semi-flexed polyamide resin (Deflex) and a conventional heat-cured resin containing cross-linking polymethyl methacrylate denture base polymers (QC-20). Materials and Methods: A vinyl polysiloxane film replicating the gap between the denture base and the metallic master model of an edentulous maxilla was weighed using an analytical balance with an accuracy of 0.0001 g for the measurement of internal adaptation. The measurements were performed immediately after surface finishing. Seven rectangular test samples measuring 65 x 10 x 3.3 mm(3) were set up for flexural strength test. Flexural strength test (three-point bending test) was performed using a universal machine under axial load at a crosshead speed of 5 mm/min. One-way ANOVA (alpha = 0.05) following by t tests was utilized in statistical analysis. Results: The difference between the flexural strength of the denture base resins of Deflex and QC-20 was found to be statistically significant. The injection-molded resin demonstrated better internal adaptation compared to the conventional heat-polymerized resin. Evaluation of the physical test results revealed that the polyamide samples were more flexible than polymethyl methacrylate and did not break during flexural strength tests. Conclusion: Some properties of denture base resins, such as resin types, internal adaptation, and mechanical strength, may play a significant role in clinical performance of complete dentures and removable partial prostheses. Because of the superior flexural strength properties and internal adaptation characteristics, Deflex may prove to be a useful alternative to conventional denture base resin.
  • Publication
    Biomechanical comparison of different prosthetic materials and posterior implant angles in all-on-4 treatment concept by three-dimensional finite element analysis
    (Walter De Gruyter Gmbh, 2022-05-20) Gürbüz, Ayhan; Güçlü, Zekiye Begüm; Gökay, Gonca Deste; Durkan, Rukiye; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; Protetik Diş Tedavisi Ana Bilim Dalı; AAM-7219-2020
    The study aimed to evaluate the biomechanical behaviors of different prosthetic materials and posterior implant angles in All-on-4 implant-supported fixed maxillary prostheses with three-dimensional (3D) finite element analysis. The model of complete edentulous maxilla was created using the Rhinoceros and VRMesh Studio programs. Anterior vertical and 17 degrees- and 30 degrees-angled posterior implants were positioned with All-on-4 design. Straigth and angled multi-unit abutments scanned using a 3D scanner. Two different prosthetic superstructures (monolithic zirconia framework and lithium disilicate veneer (ZL) and monolithic zirconia-reinforced lithium silicate (ZLS)) were modeled. Four models designed according to the prosthetic structure and posterior implant angles. Posterior vertical bilateral loading and frontal oblique loading was performed. The principal stresses (bone tissues-Pmax and Pmin) and von Mises equivalent stresses (implant and prosthetic structures) were analyzed. In all models, the highest Pmax stress values were calculated under posterior bilateral loading in cortical bone. The highest von Mises stress levels occured in the posterior implants under posterior bilateral load (260.33 and 219.50 MPa) in the ZL-17 and ZL-30 models, respectively. Under both loads, higher stress levels in prosthetic structures were shown in the ZLS models compared with ZL models. There was no difference between posterior implant angles on stress distribution occurred in implant material and alveolar bone tissue. ZLS and ZL prosthetic structures can be reliably used in maxillary All-on-4 rehabilitation.
  • Publication
    The effect of the design of a mandibular implant-supported zirconia prosthesis on stress distribution
    (Elsevier, 2021-03-04) Oyar, Perihan; Durkan, Rükiye; Deste, Gonca Gökay; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; Protetik Diş Tedavisi Ana Bilim Dalı; 0000-0002-5481-0063; AAM-7219-2020
    Statement of problem. Prosthetic complications have been frequently reported in implant supported complete-arch prosthesis. Prosthetic restorations designed with an all-on-four treatment concept and fabricated from zirconia ceramic may be used to overcome these problems.Purpose. The purpose of this biomechanical study was to evaluate the effects of cantilever length and inclination of implant on the stress distribution in bone tissue, implant, and a monolithic zirconia ceramic-lithium disilicate glass-ceramic superstructure for all-on-four prosthesis.Material and methods. All-on-four mandibular prosthesis fabricated from a zirconia and lithium disilicate glass-ceramic (LDGC) superstructure was designed with cantilever lengths of either 5 mm or 9 mm and posterior implants with a distal tilt of either 15 or 30 degrees. Stresses were evaluated with a simulated application of a static load of 600 N.Results. Increasing implant inclination from 15 to 30 degrees led to a decrease in maximum principal stress (MaxPS) values of approximately 4 to 7 MPa in cortical bone around all implants except the right anterior implant in the designs with short cantilevers and an increase in MaxPS values (approximately 3 to 19 MPa) in the same places in the designs with the long cantilevers. Increasing cantilever length from 5 to 9 mm resulted in an increase in minimum principal stress (MinPS) values of approximately 3 to 13 MPa in the cortical bone surrounding all posterior implants. In the designs with the long cantilever, MaxPS values increased approximately 3 to 4 MPa in spongy bone adjacent to the right posterior implant. An increase in cantilever length also led to higher vMS values at the first and second implant grooves in the right posterior implant in the design with the 15-degree implant tilt. An increase in implant inclination in the design with the short cantilever resulted in lower vMS values at the apex and all grooves of the left posterior implant, whereas in the design with the long cantilever, an increase in implant inclination resulted in lower stress values in the first and second grooves of the same implant. An increase in implant inclination led to in an increase in vMS values in the core structure.Conclusions. In zirconia ceramic restorations by using an all-on-four design with an LDGC superstructure, short cantilevers may be preferable because they result in a more favorable distribution of stress than long cantilevers. An increase in implant angulation from 15 to 30 degrees decreased MaxPS values in cortical bone.
  • Publication
    Wear of monolithic zirconia against different cad-cam and indirect restorative materials
    (Mosby-elsevier, 2022-10-11) Özkır, Serhat Emre; Biçer, Mehmet; Karakuş, Elif; Yılmaz, Burak; Deste, Gonca; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; 0000-0002-5481-0063; AAM-7219-2020
    Statement of problem. The wear of monolithic zirconia against enamel has been widely studied, but how zirconia affects different opposing restorative materials is not clear.Purpose. The purpose of this in vitro study was to investigate the depth of wear and volumetric loss of different restorative materials opposed by monolithic zirconia.Material and methods. Sixty-six O10x3-mm specimens (n=11) were fabricated from monolithic zirconia, zirconia reinforced ceramic, lithium disilicate ceramic, feldspathic ceramic, ORMOCER, and ceramic optimized polymer. A 2-body pin-on-disk wear test was performed by using monolithic zirconia pins. The specimens were scanned with a noncontact profilometer after the tests. The scan parameters were a frame size area of 1.5x1.5 mm, frequency of 400 Hz, and scan sensitivity of 2 gm. After the evaluation of depth and volume loss, the specimens were analyzed with a scanning electron microscope. The Kruskal-Wallis test was used to analyze the differences in wear values across the specimen groups, and pairwise comparison tests were performed with a post hoc test (a=.05). Results. Maximum depth of wear was 257.55 +/- 18.88 gm for lithium disilicate ceramic, 295.36 +/- 14.46 gm for zirconia reinforced ceramic, 421.82 +/- 214.49 gm for ORMOCER, 333.73 +/- 79.09 gm for ceramic optimized polymer, 146.27 +/- 22.86 gm for feldspathic ceramic, and 41.55 +/- 5.04 gm for monolithic zirconia. The depth of wear was not significantly different among lithium disilicate, zirconia-reinforced ceramic, ORMOCER, and ceramic optimized polymer (P<.05). However, the depth of wear of monolithic zirconia and feldspathic ceramic was less than that of other materials (P<.001). Volume loss of lithium disilicate was 1.68 +/- 0.25 mm3, 1.08 +/- 0.35 mm3 for zirconia reinforced ceramic, 4.29 +/- 2.91 mm3 for ORMOCER, 2.46 +/- 0.63 mm3 for resin ceramic, 1.07 +/- 0.09 mm3 for feldspathic ceramic, and 0.19 +/- 0.02 mm3 for monolithic zirconia. Feldspathic ceramic and monolithic zirconia had significantly less volume loss than the other groups (P<.001), and the difference between them for volume loss was statistically insignificant (P>.05).Conclusions. The tested ceramic-based materials had favorable wear resistance compared with the tested composite resinebased ones. However, the ceramics tended to crack formation than the composite resins. (J Prosthet Dent 2022;128:505-11)
  • Publication
    Mechanical response of different frameworks for maxillary all-on-four implant-supported fixed dental prosthesis: 3D finite element analysis
    (Walter de Gruyter Gmbh, 2022-08-17) Güçlü, Zekiye Begüm; Gürbüz, Ayhan; Gökay, Gonca Deste; Durkan, Rukiye; Oyar, Perihan; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; Protetik Diş Tedavisi Ana Bilim Dalı; 0000-0002-5481-0063; AAM-7219-2020
    This study's purpose is to assess the stress distribution in the peri-implant bone, implants, and prosthetic framework using two different posterior implant angles. All-on-four maxillary prostheses fabricated from feldspathic-ceramic-veneered zirconia-reinforced lithium silicate (ZLS) and feldspathic-ceramic-veneered cobalt-chromium (CoCr) were designed with 17 or 30-degree-angled posterior implants. Posterior cantilever and frontal vertical loads were applied to all models. The distribution of maximum and minimum principal stresses (sigma max and sigma min) and von Mises stress (sigma VM) was evaluated. Under posterior cantilever load, with an increase in posterior implant angle, sigma max decreased by 4 and 7 MPa in the cortical bone when ZLS and CoCr were used as a prosthetic framework, respectively. Regardless of the framework material, 17-degree-angled posterior implants showed the highest sigma VM (541.36 MPa under posterior cantilever load; 110.79 MPa under frontal vertical load) values. Regardless of the posterior implant angle, ZLS framework showed the highest sigma VM (91.59 MPa under posterior cantilever load; 218.99 MPa under frontal vertical load) values. Increasing implant angle from 17 to 30 degrees caused a decrease in sigma max values in the cortical bone. Designs with 30-degree posterior implant angles and ZLS framework material may be preferred in All-on-four implant-supported fixed complete dentures.
  • Publication
    Biaxial flexural strength and phase transformation characteristics of dental monolithic zirconia ceramics with different sintering durations: An in vitro study
    (Mosby-Elsevier, 2022-10-11) Durkan, Rukiye; Gökay, Gonca Deste; Şimşek, Hatice; Yılmaz, Burak; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; Protetik Diş Tedavisi Ana Bilim Dalı; AAM-7219-2020
    Statement of problem. Zirconia is a polymorphic metastable material which can react through a phase transformation from tetragonal to monoclinic when exposed to mechanical, physical, or chemical stimuli.Purpose. The purpose of this in vitro study was to investigate the fracture strength and phase structure of different high-translucency zirconia ceramics depending on the changes in sintering duration and thermocycling.Material and methods. Two monolithic zirconia ceramics, Katana (KAT) and NexxZr (NEX), were used to prepare disk-shaped specimens (n=66). The sintering temperature was 1500 degrees C, and 3 different sintering durations were tested: 1 hour, 2 hours (recommended by the manufacturer), and 3 hours. Thermocycling was applied to half the specimens. Fracture strength was calculated, and the specimens were analyzed with an X-ray diffractometer (XRD) to determine the level of the phase transformation. The normal distribution of the data was analyzed by using the Shapiro-Wilk test. Two-way ANOVA was used to compare multiple groups (a=.05). The Fisher least significant difference test was applied to identify significant differences in fracture strength. The paired-specimen t test was applied to perform intragroup comparisons.Results. Sintering duration significantly affected the fracture strength of KAT (P=.007). For nonthermocycled specimens, the fracture strength of NEX was significantly higher than that of KAT (P<.001). Thermocycling had a significant effect on fracture strength depending on sintering duration and zirconia ceramic interaction (P=.046).Conclusions. The sintering duration only affected the KAT zirconia, and the fracture strength of KAT decreased when sintered for 3 hours. Thermocycling decreased the fracture strength of both zirconias, except when the sintering duration was 2 hours for NEX. The fracture strength was higher for NEX than for KAT. Tetragonal-monoclinic phase transformation was not found for either zirconia according to the XRD analysis. (J Prosthet Dent 2022;128:498-504)
  • Publication
    The effect of denture cleansing solutions on the retention of precision attachments: An in vitro study
    (Mdpi, 2022-04-01) Deste Gökay, Gonca; Özkır, Serhat Emre; Wolf, Thomas Gerhard; Gökçimen, Gülsüm; Rona, Nergiz; Biçer, Mehmet; Yılmaz, Burak; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; Protetik Diş Tedavisi Ana Bilim Dalı; AAM-7219-2020
    This study aimed to investigate the effect of different cleansing solutions on the retention of precision attachments. A precision attachment patrix was embedded into acrylic resin and the matrix was placed onto the patrix. The red (high retention, 8 N), yellow (regular retention, 6 N), and green (reduced retention, 4 N) plastic matrixes of the attachments (n = 32) were soaked in three different denture cleansing solutions (sodium laureth sulfate, sodium bicarbonate-sodium perborate, sodium bicarbonate) for a duration simulating 6 months of clinical use. The control group was soaked in tap water. A universal testing machine was used to measure the retention values of attachments after they were soaked in denture cleansers. The retention values were compared among the groups with repeated-measures analysis of variance followed by the Tukey HSD test (p = 0.05). Yellow attachments were affected by sodium laureth sulfate, sodium bicarbonate-sodium perborate, and water (p = 0.012). Green attachments' retention increased after immersion in sodium laureth sulfate (p = 0.04) and water (p = 0.02). Red attachments' retention increased after immersion in sodium laureth sulfate or sodium bicarbonate-sodium perborate (p = 0.045). Water did not affect the retention of red attachments. Because sodium bicarbonate tablets did not affect the retention of attachments, clinicians may recommend their use as a cleanser. Clinicians also may inform patients using fixed and removable partial prostheses with precision attachments of a possible increase in retention after the use of sodium laureth sulfate or when using sodium bicarbonate-sodium perborate with yellow and red attachments.
  • Publication
    The effect of different abutment and restorative crown materials on stress distribution in single-unit implant-supported restorations: A 3d finite element stress analysis
    (Wiley, 2023-07-20) Gökçimen, Gülsüm; Durkan, Rukiye; Oyar, Perihan; Gökay, Gonca; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; 0000-0002-5481-0063; AAM-7219-2020
    PurposeTo evaluate the effect of restorative materials with or without resin content, modeled on zirconia and titanium abutment materials, on the stress distribution on the alveolar bone, implant, and prosthetic crowns with a 3D finite element stress analysis. Material and MethodsTitanium and zirconia abutments were combined with three implant-supported crown materials (polymer infiltrated hybrid ceramic (PICN), lithium disilicate (LD), and zirconia-reinforced lithium silicate (ZLS)) to create six experimental groups. The 40 x 30 x 20 mm alveolar bone, 3.75 x 10 mm implant, esthetic abutment, and maxillary first premolar crown bonded over the abutment were the components of the finite element models. On the lingual cusp of the crown, the 150 N occlusal loading was applied in the buccolingual direction at a 30 & DEG; angle. Equivalent von Mises stress and maximum and minimum principal stresses were used for both the qualitative and quantitative evaluation of the stress distribution of the created models. ResultsThe von Mises stress in implant and abutment did not differ according to the crown materials. The use of a zirconia abutment resulted in higher von Mises stress values in the abutment but lower stress values in the implant. The highest stress values were obtained in ZLS (196.65 MPa) and LD (194.05 MPa) crowns. The use of titanium abutments, regardless of crown materials, resulted in higher von Mises stress values in restorative crowns than in zirconia abutments. The principal stress values in alveolar bone showed similar distribution and concentration in all models. ConclusionsChanges in crown material did not affect stress distribution in the implant and peripheral bone. However, the zirconia esthetic abutment resulted in a lower stress concentration on the implant.
  • Publication
    Comparison of the effect of different metal alloys on the esthetic appearance of dentin porcelain
    (Korean Assoc Crystal Growth, Inc, 2022-02-01) Durkan, Rukiye; Oyar, Perihan; Gökcimen, Gülsüm; Gökay, Gonca Deste; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; Protetik Diş Tedavisi; 0000-0002-5481-0063; AAM-7219-2020
    The purpose of this study was to examine the effect of aurofilm masking agents applied to various metal alloys on the color of porcelain in metal-ceramic restorations (MCRs). The study was conducted with 2 different base-metal alloys (Ni-Cr, Co-Cr) and 2 different noble alloys (Pd-based, Au-Pd) used for MCRs, as well as 1 high noble alloy (Au-based) that served as a control group. Eight experimental groups (n=7) and 1 control group were used in this study. An aurofilm masking agent was applied to 4 groups (AuPdM, PdM, CoCr, NiCrM). Opaque porcelain and dentin body porcelain were applied to all groups. CIEL*a*b* color coordinates were measured. The Pd group had the highest mean a* value (-5.82); however, in comparison to the control group, the differences in a* values were statistically significant only for the Cr-Co alloy groups (CoCr and CoCrM). The Pd group had the highest mean b* value (7.89). The AE value (2.13) of the CoCr group was significantly higher than all other alloy groups. Metal alloy substrate and aurofilm masking agents significantly affected the color of porcelain MCRs. However, color differences between base-metal and noble alloys and the control group were within clinically acceptable limits (Delta E<3.5).
  • Publication
    Color stability of conventional pmma, modified mma and polyamide denture base materials in different beverages
    (Galenos Yayıncılık, 2023-09-01) Agan, Hatice; Gökay, Gonca Deste; Oyar, Perihan; Durkan, Rukiye; Gurbuz, Ayhan; DESTE GÖKAY, GONCA; Diş Hekimliği Fakültesi; Protetik Diş Tedavisi Ana Bilim Dalı; 0000-0002-5481-0063; AAM-7219-2020
    Objective: This study aimed to determine how commonly consumed beverages affected the color stability of denture base materials over time.Materials and Methods: Twenty disks (10.0-mm diameter, 2.0-mm thick) of conventional polymethylmethacrylate (PMMA) (Meliodent), modified methyl methacrylate monomer (MMA) (Bre-Crystal and Acryfee), and polyamide (Bre-Flex, Flexinylon, and T Crystal) acrylic resins with smooth and rough surfaces were prepared. The color of the specimens was measured using a colorimeter at that time (T0). Each specimen was immersed in coffee, coke, tea, and distilled water. The color of the specimens was measured again after 1-day (T1), 12-day (T2), and 36-day (T3) immersion periods. The CIE L*a*b* system was used to calculate the mean color changes for each material, which were then statistically compared using repeated measures ANOVA and Bonferroni intervals at 0.95.Results: Regardless of time or beverage, there was no significant difference between smooth and rough surfaces (p>0.05). Across all time intervals, the modified MMA (Bre-cystal) demonstrated a statistically significantly lower color difference (p<0.05). Regardless of time, modified MMA (Acryfree) and conventional PMMA (Meliodent) specimens exposed to coke demonstrated significantly lower color stability than all others (p<0.05).Conclusion: Beverages did not cause a statistically significant color change compared with distilled water after T1 and T3 periods. According to the NBS system, the color changes after the T3 period were between "slight" and "much". Modified MMA resin (Bre-Crystal) can be used as a denture base material in patients with PMMA allergy because of its high color stability in long-term use.